FIELD OF THE INVENTION
The present invention relates to a multirotor vacuum pump including at least two rotor arranged in the pump housing and cooperating with each other so that as a result of their mutual contactless movement relative to each other, working chambers, into which a to-be-pumped gas is fed, are formed.
Multirotor vacuum pumps of the type described above find a particularly wide application in chemical industry and in semiconductor technology as dry pump systems. Dry pump systems are characterized in that no oil is contained in their compression or expansion chambers for lubrication, reduction of a dead volume and similar purposes. Therefore, they are capable of producing a completely hydrocarbon-free vacuum. To obtain optimal pumping characteristics, a plurality of pump stages can be arranged in a single one after another.
In conventional multirotor vacuum pumps, two or more pistons are rotatably arranged in a single housing. The pistons are mounted on shafts supported in bearing plates arranged at one or both of opposite ends of a shaft. The rotation of the pistons is synchronized by gear sets so that a uniform rolling off of the pistons without any contact there-between, with maintaining minimal clearances, can take place. The bearings and the gear sets should be separated from the working chambers with suitable seals to prevent oil or similar working medium from penetrating into the chambers and to prevent, on the other hand, the pumped harmful gases from penetrating into the gear sets and the space, where the bearing are located, as these gases can contaminate or even destroy the lubricant. The sealing can be effectively established by using a seal gas.
In the conventional multirotor vacuum pumps, the drive motor is located outside of the pump housing and, for its connection to the main shaft, a shaft leadthrough is necessary. Dependent on the pump use and/or design, one or more rather expensive seals need be provided for the shaft leadthrough.
A serious drawback of the conventional pumps of the above-described type consists in their rather expensive construction. This results from relative large dimensions of the pump, numerous pump components, and from their rather complicated assembly. Moreover, such important components of a pump as seals between separate stages, seal gas arrangements, and elements of oil supply are often unaccessible in the known construction and need much improvement.
Accordingly, an object of the present invention is to provide a dry multirotor vacuum pump in which the foregoing drawbacks are eliminated.
A further object of the present invention is to provide a dry multirotor vacuum pump which while insuring optimal pump characteristics, would have small dimensions which would insure a space-saving and easy mounting of the pump.
A still further object of the present invention is to provide a dry multirotor vacuum pump in which the seals, the seal gas elements and the elements of the oil supply are optimally adapted to the novel concept of the pump.